Update to v5.15 kernel headers.

Kernel headers coming from:

Git: https://android.googlesource.com/kernel/common/
Branch: android-mainline
Tag: android-mainline-5.15

Test: Builds, and ran bionic unit tests on flame.
Change-Id: I86901ea6d89fb0f7384b90a47bef35d194083c24
diff --git a/libc/kernel/uapi/linux/lwtunnel.h b/libc/kernel/uapi/linux/lwtunnel.h
index f472150..e6fb536 100644
--- a/libc/kernel/uapi/linux/lwtunnel.h
+++ b/libc/kernel/uapi/linux/lwtunnel.h
@@ -29,6 +29,7 @@
   LWTUNNEL_ENCAP_BPF,
   LWTUNNEL_ENCAP_SEG6_LOCAL,
   LWTUNNEL_ENCAP_RPL,
+  LWTUNNEL_ENCAP_IOAM6,
   __LWTUNNEL_ENCAP_MAX,
 };
 #define LWTUNNEL_ENCAP_MAX (__LWTUNNEL_ENCAP_MAX - 1)